For most consumers, a preventive maintenance program for their automobile consists of nothing more than an oil change. While a regular oil change is very important, the most critical part of changing the oil is to know when to change the oil.
The interval of the oil change is often dictated by one of two factors: someone’s preference (word on the street) or the vehicle’s maintenance guide. Today’s gasoline internal combustion engine is highly advanced and so is its oil. It’s amazing how the traditional 3,000 mile oil change no longer exists, but for some reason is still highly practiced. While the vehicle owner’s manual may give recommendations of an oil change, the actual interval will depend on several other factors as well. There are many different factors that affect the frequency of an oil change such as climate, driving style, viscosity grade, and engine condition.
The same can be said for the diesel engine as well. The reason I want to touch on this subject is because in working with diesel engines every day, I still find myself talking about an engine oil change on a regular basis. The best advice on performing an adequate oil change is to have an oil analysis performed regularly.
We all know that oil lubricates the engine, but oil also does many other things that are often overlooked. Not only does oil lubricate as a means of controlling friction but also has to control contamination, temperature, corrosion, shock, wear, and pressure. Oil analysis is the only true way to put a set of “eyes” on the engine’s condition and the condition of the oil to determine when it should be changed. Today’s oil analysis programs use state-of-the-art equipment and techniques to provide the consumer with valuable information that will help them properly maintain their engine. A proper oil analysis can be somewhat intimidating to read and comprehend, however, I hope this will help you explain an oil analysis report to your customer.
First of all, there are 10 important factors that determine the condition
of oil and its service life.
1 – Viscosity
The most important factor of lubricating oil, viscosity is a measurement of resistance to flow at a specific temperature in relation to time. In an oil analysis, the used oil’s viscosity is compared to that of new oil’s viscosity to determine whether excessive thinning or thickening has occurred.
High viscosity could indicate contamination of soot, incomplete combustion, leaking head gaskets, high operating temperature or extended oil drains. Low viscosity could indicate fuel dilution, oil shear, or the use of wrong oil. The effects of high or low viscosity oil can be engine overheating, poor lubrication, restricted oil flow, metal-to-metal contact and harmful deposits. If the viscosity is wrong make sure the proper oil grade is being used and determine if there are any leaks in head gaskets or injectors.
2 – Water or Coolant Contamination
If the analysis finds water in the engine’s oil then it is entering the engine through the atmosphere or from an internal leak. Water condensation should be evaporated by the engine when operating at normal temperatures. If not, the engine may not be reaching operating temperature, causing contamination, or there are internal leaks, causing contamination. Water contamination can lead to high viscosity, engine overheating, corrosion, poor lubrication, acid formation and engine failure.
3 – Solids
This is a measurement of all solid-like substances found in the oil. For diesel engines, fuel soot is the major solid-like substance that is measured. For gasoline engines, wear debris and oil oxidation is a solid-like substance that is measured. A high concentration of solids can lead to filter clogging, engine deposits, sludge and poor lubrication resulting in short engine life.
4 – Fuel Dilution
Fuel dilution comes from unburned fuel during the combustion process which creates oil thinning. This causes the oil to lose its film strength which leads to abnormal wear. Fuel dilution leads to accelerated engine wear and shortens oil life.
5 – Fuel Soot
Fuel soot is carbon that is found in diesel engine oil. Soot is a good indicator of the engine’s combustion efficiency. Newer diesel engines have higher concentrations of fuel soot due to emissions regulations placing an emphasis on particulate emissions. Trying to reduce particulate emissions in the exhaust creates more crankcase pressure causing greater soot levels. High fuel soot levels will cause sludge, lacquer, clogged filters and poor engine performance.
6 – Oxidation
Oxidation occurs when engine oil and other components combine with oxygen to form harmful by-products. Heat, pressure and catalyst materials accelerate the oxidation of the oil. Most oils contain additives that inhibit the oxidation process. The by-products of oxidation are lacquer, corrosion and thickening to a point the oil cannot lubricate. Oxidation usually occurs from overheating, extended oil drains, blow-by and the use of the wrong oil.
7 – Nitration
Nitration is formed when blow-by gases from normal or abnormal combustion gets past the compression rings and forms with the oil. Nitration is more common in alternative fuel engines such as natural gas or propane and is highly acidic, forms deposits and oxidation. If concentration of nitration is high, check the integrity of the engine and the operating temperature.
8 – Total Acid Number (TAN)
This is the quantity of acid components found in the oil. An increase of Total Acid Number from that of a new oil should be monitored since the additives in new oil are acidic in nature. An increase in TAN comes from oxidation or water contamination. The TAN is an indicator of when the oil will need to be changed.
9 – Total Base Number (TBN)
The Total Base Number of a new oil represents a scale of the amount of additives in the oil that are capable of neutralizing the acid by-products of combustion. Example: a new oil starts with a TBN of 12. While the oil lubricates the engine to the point of its service life, the TBN decreases as the additives neutralize the acids. TBN is an indicator of when the oil needs to be changed as most diesel manufacturers recommend that oil should be drained when the TBN reaches one-half or one-third of its original value.
10 – Particle Count
Particle Count is used mostly in the analysis of hydraulic oils. Excessive particle count is an indicator of failures of a hydraulic system such as pumps, regulators, motors, valves, and controls.
The next thing to cover in an oil analysis is the elemental analysis. The elemental analysis is used to identify certain chemical elements in the used oil, where they come from and why they’re there.
Wear metals highlight problem areas; the additives determine what kind of oil was used (such as engine, hydraulic or transmission); and contamination elements determine the oil serviceability and pinpoint problem areas. Below is a list of elements and their functions.
Wear Metal Elements
Iron – Engine blocks, gears, rings, bearings, cylinder walls and cylinder heads.
Chromium – Shafts, rings and chromate from the cooling system.
Aluminum – Bushings, bearings, pistons, turbo, compressor wheels.
Copper – Bearings, bushings, oil cooler radiator.
Lead – Bearing overlay, by-product of using leaded gasoline.
Nickel – Valve stems, valve guides, ring inserts on pistons.
Silver – Bearing cages (roller bearings), turbocharger bearings, wristpin bushings.
Tin – Bearings, pistons.
Molybdenum – Piston rings, oil additives.
Zinc – Extreme pressure, antioxidant.
Phosphorus – Extreme pressure, antioxidant (phosphorus is added to extreme pressure oils to provide a protective film.
Barium – Detergent.
Sodium, Calcium, and Magnesium – Alkaline additives used to neutralize acids formed from by-products of combustion. Also have detergent qualities and corrosion inhibitors.
Boron – Rust inhibitor found mostly in coolant.
Copper – Antioxidant, used to prevent oxidation.
Contamination Elements and Their Causes
Sodium – Coolant leak or external contamination.
Silicon – Gasket material, dirt, sealants. May also be used as antifoaming agent.
Potassium – Coolant additive, most definitely a coolant leak.
The longevity of an engine is dependent on regular oil analysis especially when maintaining a fleet of equipment. Oil analysis can provide valuable information as to what engine problems may be lurking and help in maintaining proper service intervals. Any “abnormal” factors or elements will generally be red flagged on the oil analysis report, which will need to be addressed.
Oil analysis kits can be ordered from several different companies who provide the service from several locations based in the United States. Make sure the engine is at operating temperature and follow directions provided in the oil analysis bottles.
While oil samples can be taken from the oil pan drain plug, it is recommended to use what is known as a sampling gun. The sampling bottle is placed in the sampling gun and oil is drawn through a small plastic tube placed in the dipstick tube. This requires minimum effort to draw oil samples and causes less mess. Make sure to measure the plastic tube of the sampling gun with the length of the dipstick to achieve proper depth in the oil pan to draw the sample.
Courtesy Engine Builder.